In many technical applications, heat shields which must resist hot gases at 1000 to 1600 degrees are used. Particularly gas turbines of the kind used in power-generating plants and in aircraft engines have correspondingly large surfaces to be shielded by heat shields within the combustion chambers. Because of thermal expansion and large dimensions, the heat shield must be composed of a multiplicity of individual heat shield blocks, which are generally ceramic and are secured to a support structure in a manner spaced apart by a sufficient gap. This gap gives the heat shield blocks, which can also be referred to as heat shield elements, sufficient space for thermal expansion.
A heat shield of the type in question thus comprises a support structure and a number of heat shield blocks, which are secured, in particular releasably secured, to the support structure. Each of the heat shield blocks has a cold side facing the support structure and a hot side opposite the cold side, which can be subjected to a hot medium. In at least one heat shield block, at least one recess is arranged in at least one circumferential side of the heat shield block, said circumferential side connecting the cold side to the hot side, wherein an aperture, which connects the recess to the cold side, extends in the circumferential side perpendicularly to the cold side. A securing bolt can be inserted into the aperture to secure the heat shield block to the support structure, with the result that a bolt head of the securing bolt projects at least partially into the recess. At the same time, the securing bolt passes through an angled plate in a penetration region. The angled plate comprises a first limb, which extends substantially parallel to the circumferential side, and a second limb, which extends into the recess. The two limbs adjoin each other at an angle edge. Such a method of securing the heat shield block, in particular by means of two recesses on each of two opposite circumferential sides, is particularly well-suited to securing an end block of a row of heat shield blocks arranged around the combustion chamber wall. The end blocks are also referred to as dummy blocks.
EP 1 884 713 B1 discloses a heat shield of the type in question in which the heat shield blocks are secured to the support structure in rows arranged coaxially with a longitudinal axis of a combustion chamber. In this arrangement, the heat shield blocks of one row are held by holding elements, which are inserted into a securing groove extending in the support structure, wherein the holding elements of the subsequent heat shield blocks are inserted into the securing groove after the holding elements of the preceding heat shield block have been secured, and they lock the preceding holding elements. In the case of the known heat shield, the dummy blocks are fixed on the support structure by means of a fastener that can be screwed into the support structure. On two opposite circumferential sides of the heat shield block, said sides connecting the cold side to the hot side, these dummy blocks have two recesses. In association with each of these recesses there is an aperture in the circumferential side, said aperture extending perpendicularly to the cold side and connecting the recess to the cold side. To secure the dummy block to the support structure, a securing bolt is inserted into each of the four apertures, with the result that a bolt head of the securing bolt projects into the recess. To ensure better distribution of the pressure exerted on the heat shield block by the bolt head, an angled plate is arranged underneath the bolt head. The securing bolt passes through the angled plate in a penetration region, with the result that the angled plate extends underneath the bolt head by means of a limb projecting into the recess and covers the aperture in which the securing bolt extends by means of a limb extending substantially parallel to the circumferential side. Slipping of the securing bolt out of the aperture can lead to a loss of the heat shield block. During operation, this can give rise to damage to the combustion chamber lined with the heat shield.